This research is designed to estimate the medical care costs of drug abuse in a hospital setting. The epidemiology of the medical complications of drug abuse will be established by abstracting the medical charts of both inpatients and outpatients in inner-city acute care hospitals. The hospitals are located in communities in New York City known to have large drug-abusing populations. A compendium of medical complications secondary to drug abuse and the associated use of medical resources in their diagnoses and treatment will be established. The medical complications will be recorded as specific disease entities (e.g. cellulitis) and aggregated into a broader taxonomy (e.g. infections). Medical resources will be recorded as categories as inpatient days, outpatient visits, surgical procedures, intensive care days, and ancillary tests. Medical complications will be related to resource use and medical care costs of drug abuse will be estimated for the specific disease entities and the broader taxonomy. The research methodology is based upon a pilot study conducted by the investigators at Harlem Hospital, New York City. Here, patient records were systematically reviewed by one of the investigators, a physician, for indications of medical complications secondary to drug abuse, self-reports of current abuse, and clinical documentation of abuse. Based upon the pilot study and a review of clinical studies, a diagnostic index will be developed and used as a research tool by medical chart abstractors. The abstractors will be trained by the investigators and their work will be periodically monitored by the physician investigator. Data will be collected over a one year period and recorded on pre-coded forms. In addition to the estimation of medical care costs, data analysis will include frequency distributions and cross-tabulations of the principal categories of medical complications